Prior to the start of winter we made note of the fact that a La Nina had set up in the western & central Pacific Ocean and how that could translate to a cold and somewhat snowier than average season in North Central Wisconsin. To this point, that forecast has held up with December & most likely January going down anywhere from 1-3 degrees below average and snowfall being a little over 2" above normal.
However, this has been far from a typical La Nina weather pattern for those folks in the Mid-Atlantic & Northeastern U.S. The second major winter storm of the season blasted locations from the western suburbs of D.C. to Philly, New York City and Boston with anywhere from 8-20" of snow. Yes, this was another nor'easter that blew up off the Virginia/Delaware coast before trucking northeast, but it was not a text book example. More on that in a moment. First off let me put into perspective the amount of snow that has fallen in some of the big cities in the Northeast, and compare it to us in Wausau.
So far this winter, Wausau has picked up 36.7", only a little above average. However to this point, Philadelphia has gotten 37.8", New York City 56.1", Newark, NJ 62.8" and Boston 60.3". Usually up to the last week in January, Philly typically sees 7.7", NYC ~10", Newark, NJ ~11" and Boston 19.8". I believe for all of these cities, they have already surpassed the average snowfall for the season and are now waiting to see if they will challenge the numbers they put up last winter in the total snowfall category (which for most of them were at record high amounts).
What has lead to the heavy snowfall in this part of the country? Well, the jet stream simply put. It has been digging far enough to the south to keep cold enough air in place and aligning just right for nor'easters to take a favorable track up along the coast, approximately 100-150 miles away from shore, to put these locations in the sweet spot for the snow to pile up. In all of my years living back in South Jersey, getting over a foot of snow once every 4-5 years was a lot, but it seems since the early 2000s, we have seen a ramping up of the heavy snowfalls that have hit. What is more common with nor'easters when they traverse up the east coast is a mix to rain scenario in the major cities on east, while the precip stayed mainly snow to the north and west, leading to the heavier snow.
I mentioned this latest storm was far from normal in the realm of nor'easters. Here's why. First off for there to be a major nor'easter, a good rule of thumb is to "predict the high, predict the storm". Ideally, a polar high pressure should be stationed up to the northeast, let's say 200-300 miles off the Maine or Nova Scotia coast. This is important to lock in cold air in the Northeast & Mid-Atlantic for precipitation to stay primarily snow in the big cities. Second, the track of the low (as mentioned earlier) needs to be far enough off the coast to keep the cold air in place but not too far east that the precipitation misses the area entirely. In this scenario, there was a high to the northeast, but was a ways out there, more like 400 miles off the Nova Scotia coast. Thus not that great for keeping the cold air in place the whole time. The next interesting wrinkle with this storm was that it was a double barrel low. In other words, one wave of low pressure rolled through the region late Tuesday night into Wednesday morning, followed by the second, more intense low dumping the snow late Wednesday afternoon into early Thursday morning.
With that in mind, I was keeping track of what the various weather models were spitting out leading up to this storm from Tuesday through Thursday. A lot of them did initially show cold enough air for the precipitation to start off as snow, but also showed that accumulations with the first round of precipitation would be muted due to a change over to a mix/rain as a warm front pushed north. Well, that front never made it past central Delaware and the overrunning moisture was coming down heavy enough that evaporational cooling allowed mostly snow to fall into Wednesday morning for the Philadelphia area. So instead of a slushy 1-3", it added up to 3-6 from the city on west, with 1-2" to the south and east. That might not sound like a big deal, but it was the first sign that round 2 of the storm was going to be a possible dozy.
Back to the weather model depictions. It seemed odds were good that that second low would produce the heaviest snow and do so from Wednesday evening into Thursday morning. The main questions were how quickly would the light rain/mix in the area go to snow and then how heavy would the snowfall end up being? Well safe to say that cold enough air swept right back into the Philly area a couple hours after sunset and thundersnow was occurring during the evening with rates of accumulation in the range of 2-3" per hour. This same intense snow translated up to the north in NYC and Boston, dumping significant amounts heading toward daybreak on Thursday. Now unlike the last storm that impacted this part of the country the day after Christmas, not everyone experienced blizzard conditions. But looking through the surface observations, Newark, NJ, New York City, and Hartford had visibilities under a .25 mile for at least 3 hours...thus the Blizzard of January 2011 could go down in the books for those locales.
Of course, with February and early March still to come, there is the risk that another nor'easter or two could form and take aim at the eastern seaboard. Only time and the weather pattern will dictate whether this actually comes together like it has already this winter. Needless to say, these folks may end up with more snow by the time all is said and done than us here in North Central Wisconsin.
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